1. Technical Field of the Invention
The present invention generally relates to optical networks. More particularly, and not by way of any limitation, the present invention is directed to a system and method for routing stability-based integrated traffic engineering (“RITE”) for a Generalized Multi-Protocol Label Switching (“GMPLS”) network.
2. Description of Related Art
GMPLS optical networks generally include a plurality of edge nodes, comprising MPLS routers, that have appropriate opto-electrical interfaces for converting incoming electrical signals to optical signals (E/O interfaces) at an “ingress node” and for converting optical signals to electrical signals (O/E interfaces) at an “egress node”. Traffic is routed between an ingress and egress node pair via optical cross connects (“OXCs”) located throughout the network. OXCs are nodes that lack any sort of electrical capability; they simply route optical signals from one node to another. A light channel (“LC”), or Label Switched Path (“LSP”), is an optical communications channel from an ingress node to an egress node via one or more intermediate nodes, which may comprise OXCs as well as edge nodes, in some cases.
High-priority (“HP”) and low-priority (“LP”) traffic trunks are characterized by the start and end times of their active resource utilization, also known as “lifetimes”. HP traffic trunks need absolute routing stability. In contrast, LP traffic trunks may be rerouted; that is, traffic may be transported between an ingress/egress node pair via an LC on which it was not originally mapped. Rerouting stability is a measure of how many times a traffic trunk is rerouted in its lifetime. Lifetimes of traffic trunks are measured in time units (e.g., seconds, minutes), and are typically drawn from a probabilistic distribution.
A direct LC is an LC that is established between an ingress/egress node pair that constitutes only a single LC. In contrast, a multi-hop LSP constitutes one or more edge nodes as intermediate termination points of the LCs and may comprise multiple wavelengths. The traffic undergoes O/E/O conversion at the intermediate edge nodes. HP and LP requests are requests for bandwidth allocation and appropriate mapping on the LCs for HP and LP traffic trunks, respectively. Mapping could be on existing, or established, LCs or on new LCs that are established dynamically.
Static provisioning of light channels in a GMPLS optical network is generally cumbersome and time-consuming and often leads to underutilization of resources if traffic demands within the network vary with time. In order to adapt to the changing traffic demands for optimal resource utilization, schemes that dynamically establish and teardown optical channels are highly desirable. However, this “make-and-break” of optical channels often results in the rerouting of existing traffic that can lead to better utilization of resources. Rerouting for individual traffic trunks can affect many relevant quality of service (“QoS”) measures, such as delay and jitter, and may lead to degradation of throughput. For example, Transmission Control Protocol (“TCP”) applications that do not have large buffers for reordering of the out-of-sequence packets may trigger retransmission of many packets. Delay and jitter are critical to real-time applications and also get affected as a result of rerouting of traffic trunks. In the case of non-packet-based Time Division Multiplex (“TDM”) signals, rerouting may translate into disruption of ongoing signals. Traffic Engineering (“TE”) procedures should address these issues in the context of dynamic wavelength assignment and traffic mapping in order to make optimal use of the optical resources.
Currently, only general TE frameworks for GMPLS in optical networks have been proposed. No solutions currently exist that address the above-noted TE issues with respect to rerouting of traffic.